High breakdown voltage and high electron mobility has made GaN an ideal candidate for high-power transistor applications. Furthermore, the large bandgap of GaN means that the performance of GaN transistors may be maintained at much higher temperatures than other conventional semiconductor options. Applications include, but are not limited to, microwave radio-frequency amplifiers, high voltage switching devices, and power supplies. One mass market application is the microwave source from microwave ovens (to replace magnetrons).
Despite their potential for ubiquitous use in consumer electronics, GaN based devices still suffer from several limitations as a result of the high-voltage environments they are used in. Device layers in GaN transistors may build up charge during use, resulting in changing device performance due to electric field redistribution, and thermal stressing. In the worst case, HFET devices may critically fail due to dielectric breakdown or cracking of device layers.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.